This invention relates to a pipetting apparatus and more particularly to a pipetting apparatus of the type which is called as a micro-pipetting apparatus that is adapted to dispence a predetermined small amount of liquid such as five to two hundred micro liters with a high degree of accuracy and reproducibility.
One of the prior art micro-pipetting apparatus includes a glass capillary tube having one or more scale lines on the middle portion thereof and a rubber tube attached to the upper end thereof. An operator of the apparatus places the free end of the rubber tube in his mouth and sucks the liquid sample into the capillary tube up to a predetermined scale line and, thereafter, blows the liquid sample out from the capillary tube. Although the apparatus is very simple in construction, it is difficult to assure that the liquid sample has been sucked accurately to the scale line and to blow out the liquid sample completely from the capillary tube, thus decreasing accuracy of the apparatus. Further, it sometimes occurs to mix saliva of the operator into the liquid sample in blowing out the liquid sample which deteriorates the quality of the sample, and to flow the liquid sample such as blood into the mouth of the operator in sucking up the liquid sample which might cause a bacterium infection.
Another prior art micro-pipetting apparatus comprises a cylinder-piston means incorporated in the apparatus which is manually operated for sucking up and ejecting out the liquid sample into and from a liquid receiving tube such as a glass capillary tube or the like attached to the lower end of the apparatus, but it has also been difficult to eject the liquid sample completely from the liquid receiving tube thus deteriorating the accuracy of the apparatus.